<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Tiers</title>
<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
<link rel="home" href="../../../../index.html" title="Chapter 1. Fusion 2.2">
<link rel="up" href="../functions.html" title="Functions">
<link rel="prev" href="make_map.html" title="make_map">
<link rel="next" href="list_tie.html" title="list_tie">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td>
<td align="center"><a href="../../../../../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="make_map.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="list_tie.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="fusion.container.generation.functions.tiers"></a><a class="link" href="tiers.html" title="Tiers">Tiers</a>
</h5></div></div></div>
<p>
            Tiers are sequences, where all elements are non-const reference types.
            They are constructed with a call to a couple of <span class="emphasis"><em>tie</em></span>
            function templates. The succeeding sections document the various <span class="emphasis"><em>tier</em></span>
            flavors.
          </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
                <a class="link" href="list_tie.html" title="list_tie"><code class="computeroutput"><span class="identifier">list_tie</span></code></a>
              </li>
<li class="listitem">
                <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a>
              </li>
<li class="listitem">
                <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">map_tie</span></code></a>
              </li>
<li class="listitem">
                <a class="link" href="deque_tie.html" title="deque_tie"><code class="computeroutput"><span class="identifier">deque_tie</span></code></a>
              </li>
</ul></div>
<p>
            Example:
          </p>
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span> <span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span> <span class="keyword">double</span> <span class="identifier">d</span><span class="special">;</span>
  <span class="special">...</span>
<a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">,</span> <span class="identifier">c</span><span class="special">,</span> <span class="identifier">d</span><span class="special">);</span>
</pre>
<p>
            The <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a> function creates
            a <a class="link" href="../../vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a>
            of type <code class="computeroutput"><a class="link" href="../../vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;,</span> <span class="keyword">char</span><span class="special">&amp;,</span> <span class="keyword">double</span><span class="special">&amp;&gt;</span></code>. The same result could be achieved
            with the call <a class="link" href="make_vector.html" title="make_vector"><code class="computeroutput"><span class="identifier">make_vector</span></code></a>(<a href="http://www.boost.org/libs/core/ref.html" target="_top"><code class="computeroutput"><span class="identifier">ref</span></code></a>(i), <a href="http://www.boost.org/libs/core/ref.html" target="_top"><code class="computeroutput"><span class="identifier">ref</span></code></a>(c), <a href="http://www.boost.org/libs/core/ref.html" target="_top"><code class="computeroutput"><span class="identifier">ref</span></code></a>(d)) <a href="#ftn.fusion.container.generation.functions.tiers.f0" class="footnote" name="fusion.container.generation.functions.tiers.f0"><sup class="footnote">[11]</sup></a>.
          </p>
<p>
            A <span class="emphasis"><em>tie</em></span> can be used to 'unpack' another tuple into
            variables. E.g.:
          </p>
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span> <span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span> <span class="keyword">double</span> <span class="identifier">d</span><span class="special">;</span>
<a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">,</span> <span class="identifier">c</span><span class="special">,</span> <span class="identifier">d</span><span class="special">)</span> <span class="special">=</span> <a class="link" href="make_vector.html" title="make_vector"><code class="computeroutput"><span class="identifier">make_vector</span></code></a><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="char">'a'</span><span class="special">,</span> <span class="number">5.5</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">i</span> <span class="special">&lt;&lt;</span> <span class="string">" "</span> <span class="special">&lt;&lt;</span>  <span class="identifier">c</span> <span class="special">&lt;&lt;</span> <span class="string">" "</span> <span class="special">&lt;&lt;</span> <span class="identifier">d</span><span class="special">;</span>
</pre>
<p>
            This code prints 1 a 5.5 to the standard output stream. A sequence unpacking
            operation like this is found for example in ML and Python. It is convenient
            when calling functions which return sequences.
          </p>
<h6>
<a name="fusion.container.generation.functions.tiers.h0"></a>
            <span class="phrase"><a name="fusion.container.generation.functions.tiers.ignore"></a></span><a class="link" href="tiers.html#fusion.container.generation.functions.tiers.ignore">Ignore</a>
          </h6>
<p>
            There is also an object called <span class="emphasis"><em>ignore</em></span> which allows
            you to ignore an element assigned by a sequence. The idea is that a function
            may return a sequence, only part of which you are interested in. For
            example:
          </p>
<pre class="programlisting"><span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span>
<a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a><span class="special">(</span><span class="identifier">ignore</span><span class="special">,</span> <span class="identifier">c</span><span class="special">)</span> <span class="special">=</span> <a class="link" href="make_vector.html" title="make_vector"><code class="computeroutput"><span class="identifier">make_vector</span></code></a><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="char">'a'</span><span class="special">);</span>
</pre>
<div class="footnotes">
<br><hr style="width:100; text-align:left;margin-left: 0">
<div id="ftn.fusion.container.generation.functions.tiers.f0" class="footnote"><p><a href="#fusion.container.generation.functions.tiers.f0" class="para"><sup class="para">[11] </sup></a>
              see <a href="http://www.boost.org/libs/core/ref.html" target="_top">Ref utility</a>
              for details about <code class="computeroutput"><span class="identifier">ref</span></code>
            </p></div>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman,
      Dan Marsden, Tobias Schwinger<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="make_map.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="list_tie.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
